In recent years, advances in technology, as well as ever evolving tastes in style, have led to substantial changes in the design of automobiles. One of the changes involves the complexity, as well as the power usage, of the electrical systems within automobiles, particularly alternative fuel vehicles, such as hybrid, electric, and fuel cell vehicles. Such alternative fuel vehicles typically use an electric motor, perhaps in combination with another actuator, to drive the wheels.
For high speed applications, such as use in an alternative fuel vehicle, a sufficiently large “pulse ratio” is required to provide important information about the performance of the motor, such as motor terminal currents and rotor position. The pulse ratio may be defined as the ratio of the switching frequency of the inverter, which converts direct current (DC) power from a battery to alternating current (AC) power, to the fundamental frequency of the motor.
In recent years, the number of poles and the operating speeds of the motors used in such vehicles have been increased. As a result, the fundamental frequencies of the motors have also increased, which has consequently decreased the pulse ratios. One of the problems encountered during the operation of these motors is the occurrence of oscillations, known as “beat frequency oscillations,” in the stator current due to Non-triplen Odd Harmonics (NTOHs) in the pulse ratio. These oscillations can hinder the performance of the motor, and, over long periods of time, damage the transistors within the inverters.
Accordingly, it is desirable to provide a method and system for operating a motor that prevents the oscillations due to the NTOHs. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.